1. Field of the Invention
This invention relates to an ink composition and a recording method which use the same, particularly an ink composition suitable as an ink for ink jet recording use which can further improve ozone-proof property and inhibit changes in hue, and a recording method which use the same.
2. Description of the Related Art
In recent years, with the popularization of computers, ink jet printers are broadly used, not only at offices but also at homes, for the purpose of printing letters and pictures on paper, films, cloth and the like.
The ink jet recording method includes a system in which droplets are discharged by applying pressure using a piezo element, a system in which droplets are discharged by generating bubbles in the ink with heat, a system in which ultrasonic wave is used, and a system in which droplets are sucked and discharged by electrostatic force. As the ink for these ink jet recording system, water-color ink, oil base ink or solid (melt type) ink is used.
Among these inks, water-color ink is relatively superior to oil base ink and solid (melt type) ink, in terms of the possibility of taking a triangular position regarding its production, handling, odor, safety and the like, so that it is now the main stream of the ink for ink jet recording use.
For the dyes to be used in these inks for ink jet recording use, there are requirements such as high solubility in solvent (ink medium), ability to perform high density recording, proper hue, excellent solidity for light, heat, air, water and drugs, good fixing ability to and difficulty in soaking into image receiving material, excellent shelf life as ink, no toxicity, high purity and inexpensive availability. However, it is extremely difficult to find a dye which satisfies the aforementioned various requirements at a high level. Particularly, the excellent hue and the solidity conflict in most cases, for example, it is difficult to obtain a coloring material for magenta ink use which satisfies the aforementioned various requirements, and it is particularly difficult to find a dye that has both of good magenta hue and light solidity capable of standing against oxidizing atmosphere.
Thus, though various dyes and pigments have already been proposed as compounds for ink jet use and are now actuary used, it is the present situation that a dye which satisfies all of the aforementioned requirements has not been found yet.
In the case of the conventionally well known dyes and pigments having color index (C.I.) numbers, it is difficult to simultaneously obtain both of the hue and solidity required for the ink for ink jet recording use.
As a dye capable of improving solidity, azo dyes derived from an aryl amine and a 5-membered heterocyclic amine have been proposed, which are described in JP-A-55-161856 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). However, since these dyes have undesirable hues in the yellow and cyan regions, they have a problem of worsening color reproducibility.
Inks for ink jet recording use have been disclosed in JP-A-61-36362 and JP-A-2-212566, with the aim of simultaneously obtaining the hue and light solidity. However, the dye used in each of the official gazettes is insufficient in terms of its solubility in water when used as a water-soluble ink. In addition, when the dye described in each of the official gazettes is used as a water-soluble ink for ink jet use, it also causes a problem in terms of wet heat solidity.
As a means for solving these problems, improved magenta pigments and inks which used the same proposed, as described in JP-T-11-504958 (the term “JP-T” as used herein means an “unexamined published international patent application in Japanese”), JP-A-2002-371079 and JP-A-2002-371214. However, these inks for ink jet recording use. were not sufficient in terms of their color reproducibility and solidity of output images.
In addition, it was revealed that shelf life of images is considerably worsened in some cases when images are recorded on a ink jet-exclusive use glossy paper for photographic image quality use and applied to an indoor wall or the like. The present inventors guess that this phenomenon is due to ozone and the like certain oxidizing gasses in the air. Also, this phenomenon hardly occurs when flow of the air is blocked by a treatment such as sealing in a glass frame, but its use conditions are limited.
Since this phenomenon is particularly significant on the ink jet-exclusive use glossy paper for photographic image quality use, this is a serious problem for the current ink jet recording system in which the photographic image quality is one of the important characteristics.
On the other hand, the ink for ink jet recording use which uses the aforementioned water-soluble dye has the aforementioned advantages, but on the contrary, it has a problem of generating changes in hue at the time of fading, so that its resolution is required.